How to Download and Install IOS on Cisco Catalyst 3750 Switches

If you are using Cisco Catalyst 3750 switches in your network, you might want to keep them updated with the latest Cisco IOS software. IOS, or Internetwork Operating System, is the software that runs on Cisco routers and switches, providing network services and protocols. Updating your IOS software can improve your network performance, security, and reliability, as well as fix bugs and add new features.

In this article, we will show you how to download and install IOS on Cisco Catalyst 3750 switches, which are innovative switches that combine industry-leading ease of use and high resiliency for stackable switches. They feature Cisco StackWise technology, a 32-Gbps stack interconnect that allows customers to build a unified, highly resilient switching system, one switch at a time.

Prerequisites

Before you start the IOS upgrade process, you need to make sure that you have the following hardware and software requirements:

A PC or workstation with a TFTP or RCP server application installed. You will use this to transfer the IOS image file from your PC to the switch. You can download a TFTP server for Windows from here.
A console cable (usually a flat black cable) that connects the console port of the switch to the COM port of your PC. You will use this to establish a console session to the switch.
A valid Cisco IOS image file for your switch model and feature set. You can obtain this from Cisco Software Central. Make sure that you choose the correct image file that supports your hardware and software features, and that your switch has enough memory to run it. You can also verify the integrity of the image file by checking its MD5 checksum.

Steps to Download and Install IOS on Cisco Catalyst 3750 Switches

Once you have all the prerequisites ready, you can follow these steps to download and install IOS on your switch:

Step 1: Establish a console session to the switch

Connect your PC to the switch using the console cable. Then, open a terminal emulation program (such as PuTTY or HyperTerminal) on your PC and configure it with these settings:

Parameter	Value
Baud rate	9600 bps
Data bits	8
Parity	None
Stop bits	1
Flow control	None

Press Enter a few times until you see the switch prompt. If you are prompted for a username and password, enter them accordingly. If you do not have them, contact your network administrator. You should see a prompt like this:

Switch>

If you are in user mode, enter the enable command to enter privileged mode. You should see a prompt like this:

Switch#

Step 2: Verify the current IOS version and feature set

To check the current IOS version and feature set running on your switch, enter the show version command. You should see an output like this:

Switch#show version Cisco IOS Software, C3750 Software (C3750-IPSERVICESK9-M), Version 12.2(55)SE10, RELEASE SOFTWARE (fc2) Technical Support: http://www.cisco.com/techsupport Copyright (c) 1986-2016 by Cisco Systems, Inc. Compiled Thu 21-Jan-16 08:54 by prod_rel_team Image text-base: 0x01000000, data-base: 0x02F00000 ROM: Bootstrap program is C3750 boot loader BOOTLDR: C3750 Boot Loader (C3750-HBOOT-M) Version 12.2(44)SE5, RELEASE SOFTWARE (fc1) Switch uptime is 1 hour, 23 minutes System returned to ROM by power-on System image file is "flash:c3750-ipservicesk9-mz.122-55.SE10.bin" ...

The line that starts with System image file shows the name and location of the IOS image file. In this example, the image file is c3750-ipservicesk9-mz.122-55.SE10.bin and it is stored in the flash memory of the switch. The name of the image file also indicates the IOS version and feature set. In this example, the IOS version is 12.2(55)SE10 and the feature set is IP Services.

Step 3: Delete the old IOS image file from the flash memory

To free up some space on the flash memory for the new IOS image file, you need to delete the old IOS image file. To do this, enter the delete flash: command, where is the name of the old IOS image file. For example:

Switch#delete flash:c3750-ipservicesk9-mz.122-55.SE10.bin Delete filename [c3750-ipservicesk9-mz.122-55.SE10.bin]?  Delete flash:c3750-ipservicesk9-mz.122-55.SE10.bin? [confirm]

Press Enter to confirm the deletion. You should see a message like this:

Deleting flash:c3750-ipservicesk9-mz.122-55.SE10.bin...done

Step 4: Copy the new IOS image file to the flash memory using TFTP or RCP

To copy the new IOS image file from your PC to the switch, you need to use either TFTP or RCP protocol. TFTP is a simple and widely used protocol for transferring files over a network, but it does not provide any security or authentication features. RCP is a more secure and reliable protocol that uses SSH for encryption and authentication, but it requires more configuration on both ends.

In this article, we will use TFTP as an example, but you can also use RCP if you prefer. To copy the new IOS image file using TFTP, follow these steps:

On your PC, make sure that your TFTP server application is running and that the new IOS image file is in the root directory of the TFTP server.
On your switch, enter the copy tftp flash command. You will be prompted for some information, such as the IP address of your PC, the name of the IOS image file, and the destination filename on the flash memory. For example:

Switch#copy tftp flash Address or name of remote host []? 192.168.1.100 Source filename []? c3750-ipbasek9-mz.150-2.SE11.bin Destination filename [c3750-ipbasek9-mz.150-2.SE11.bin]?  Accessing tftp://192.168.1.100/c3750-ipbasek9-mz.150-2.SE11.bin... Loading c3750-ipbasek9-mz.150-2.SE11.bin from 192.168.1.100 (via Vlan1 ): !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! [OK - 33509312 bytes] 33509312 bytes copied in 120.456 secs (278213 bytes/sec)

Wait until the file transfer is complete and verify that the new IOS image file is in the flash memory by entering the dir flash: command. You should see an output like this:

Switch#dir flash: Directory of flash:/     2  -rwx        3350   Mar 1 1993 00:04:05 +00:00  config.text     3  -rwx        2072   Mar 1 1993 00:04:05 +00:00  private-config.text     4  -rwx    33509312   Jun 20 2023 17:15:23 +00:00  c3750-ipbasek9-mz.150-2.SE11.bin     5  drwx         192   Mar 1 1993 00:05:42 +00:00  c3750-ipbasek9-mz.122-55.SE10     ...

Step 5: Configure the boot variable to load the new IOS image on startup

To make the switch load the new IOS image on startup, you need to configure the boot variable with the name and location of the new IOS image file. To do this, enter the conf t command to enter global configuration mode, and then enter the boot system flash: command, where is the name of the new IOS image file. For example:

Switch#conf t Enter configuration commands, one per line. End with CNTL/Z. Switch(config)#boot system flash:c3750-ipbasek9-mz.150-2.SE11.bin Switch(config)#end Switch#

To verify that the boot variable is set correctly, enter the show boot command. You should see an output like this:

Switch#show boot BOOT path-list      : flash:c3750-ipbasek9-mz.150-2.SE11.bin Config file         : flash:/config.text Private Config file : flash:/private-config.text Enable Break        : no Manual Boot         : no HELPER path-list    : Auto upgrade        : yes Auto upgrade path   : NVRAM/Config file buffer size:       : 524288 Timeout for Config Download:          : 0 seconds Config Download via DHCP:          : disabled (next boot: disabled)

Step 6: Reload the switch and verify the upgrade

To apply the changes and load the new IOS image, you need to reload the switch. To do this, enter the reload command and confirm it. For example:

Switch#reload Proceed with reload? [confirm]

The switch will reboot and load the new IOS image. To verify that the upgrade was successful, enter the show version command again and check the IOS version and feature set. You should see an output like this:

Switch#show version Cisco IOS Software, C3750 Software (C3750-IPBASEK9-M), Version 15.0(2)SE11, RELEASE SOFTWARE (fc3) Technical Support: http://www.cisco.com/techsupport Copyright (c) 1986-2018 by Cisco Systems, Inc. Compiled Mon 26-Feb-18 12:49 by prod_rel_team Image text-base: 0x01000000, data-base: 0x02F00000 ROM: Bootstrap program is C3750 boot loader BOOTLDR: C3750 Boot Loader (C3750-HBOOT-M) Version 12.2(44)SE5, RELEASE SOFTWARE (fc1) Switch uptime is 5 minutes System returned to ROM by power-on System image file is "flash:c3750-ipbasek9-mz.150-2.SE11.bin" ...

Conclusion

In this article, we have shown you how to download and install IOS on Cisco Catalyst 3750 switches using TFTP protocol. By following these steps, you can keep your switches updated with the latest IOS software and enjoy improved network performance, security, and reliability.

Here are some tips and best practices for IOS upgrade:

Always backup your switch configuration before upgrading IOS.
Always verify the integrity of the IOS image file by checking its MD 5 checksum and comparing it with the one provided by Cisco.
Always use a reliable and secure protocol for transferring the IOS image file, such as RCP or SCP.
Always test the new IOS image on a non-production switch before deploying it to the production network.
Always follow the Cisco documentation and guidelines for IOS upgrade, which you can find here.

FAQs

Here are some frequently asked questions and answers about IOS upgrade on Cisco Catalyst 3750 switches:

Q1: What is Cisco StackWise technology and how does it affect IOS upgrade?

A1: Cisco StackWise technology is a feature that allows up to nine Catalyst 3750 switches to operate as a single logical unit, sharing a common control plane, data plane, and management plane. This provides high availability, scalability, and simplified management for stackable switches. When you upgrade IOS on a switch stack, you need to make sure that all the stack members are running the same IOS version and feature set. You also need to use the archive download-sw command instead of the copy tftp flash command to copy the IOS image file to all the stack members simultaneously.

Q2: How can I recover from a corrupted or failed IOS upgrade?

A2: If your switch fails to boot up after an IOS upgrade, you might have a corrupted or incompatible IOS image file on the flash memory. In this case, you need to use the ROMmon mode to recover from the problem. ROMmon, or ROM monitor, is a low-level mode that allows you to perform basic troubleshooting and maintenance tasks on your switch. To enter ROMmon mode, you need to interrupt the boot process by pressing the Mode button on the front panel of the switch. Then, you can use ROMmon commands to erase the flash memory, download a new IOS image file using Xmodem protocol, and boot up the switch with the new image. For more details on how to use ROMmon mode, refer to this document.

Q3: How can I check the free space and memory usage on the flash memory?

A3: To check the free space and memory usage on the flash memory, you can use the show flash: command. This command will display information such as the total size, available size, used size, erase size, and directory of files on the flash memory. For example:

Switch#show flash: Directory of flash:/     2  -rwx        3350   Mar 1 1993 00:04:05 +00:00  config.text     3  -rwx        2072   Mar 1 1993 00:04:05 +00:00  private-config.text     4  -rwx    33509312   Jun 20 2023 17:15:23 +00:00  c3750-ipbasek9-mz.150-2.SE11.bin     ... 32514048 bytes total (0 bytes free)

Q4: How can I use a web-based device manager or network assistant to upgrade IOS?

A4: If you prefer a graphical user interface (GUI) over a command-line interface (CLI) for IOS upgrade, you can use either a web-based device manager or network assistant. A web-based device manager is a built-in web server on your switch that allows you to access and configure your switch using a web browser. A network assistant is a standalone application that allows you to manage multiple switches and routers in your network using a single interface. Both tools provide an easy and intuitive way to upgrade IOS on your switch. For more details on how to use these tools, refer to this document and this document.

Q5: How can I choose the best IOS release and feature set for my switch?

A5: Choosing the best IOS release and feature set for your switch depends on several factors, such as your hardware model, software requirements, network environment, and budget. Generally speaking, you should choose an IOS release that is stable, secure, and compatible with your hardware and software features. You should also choose an IOS feature set that meets your network needs and does not exceed your memory and license limitations. To help you choose the best IOS release and feature set for your switch, you can use tools such as Cisco Feature Navigator, Cisco Software Advisor</a ), and Cisco Software Research Tool.

Thank you for reading this article. I hope you have learned how to download and install IOS on Cisco Catalyst 3750 switches. If you have any questions or feedback, please leave a comment below. Have a great day!

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